[imp] Isis: Hide dotted outline on tabs

## Steps to reproduce the issue

backend - menus - select menu item - click item - click on any tab

## Expected result

![2](https://cloud.githubusercontent.com/assets/876623/4600442/8e59a738-50d4-11e4-8692-4ef0576cdc0d.jpg)

## Actual result

![1](https://cloud.githubusercontent.com/assets/876623/4600445/99e59058-50d4-11e4-8049-8dae837daa1a.jpg)

## System information (as much as possible)

All Joomla version

## Additional comments